Introduction

VideoScope is a software waveform and vector scope for Power Macintosh G3 computers with video input capabilities. It performs realtime luminance and chrominance analysis of any video source, QuickTime movie or still image, allowing you to adjust your video digitizer’s image settings to obtain the best possible video quality.

Contents

• Video and Scope Displays

• Front Panel Controls

• Menu Commands

• Other Features

Incoming video is shown in RGB color space in the RGB Video display. The corresponding waveforms and vectors are shown in YUV color space in the YUV Scope display. The YUV Scope display has four modes: Y, U and V waveform displays and a UV vector display.

Waveform Displays

In the Y, U and V waveform modes, the horizontal axis represents the horizontal position of the sampled pixels in the source, and the vertical axis represents Y, U or V, depending on the selected mode. The intensity of the scope display at any given position is proportional to the number of pixels with that Y, U or V value at that horizontal position in the source. A color mode is also available where the waveform color corresponds to the actual color of the sampled pixels.

Fig 1. Scope display in Y waveform mode

Vector Displays

In the UV vector mode, the horizontal axis represents U, and the vertical axis represents V. This results in a hexagonal color space diagram, with 0% saturated white, gray and black located at the center and 100% saturated red, magenta, blue, cyan, green and yellow located at the vertices. Pixels from the source are displayed at their respective positions within this color space. A color mode is also available where the vector color corresponds to the actual color of the sampled pixels.

Fig 2. Scope display in UV vector mode

Color Space Conversions

When converting RGB color space to YUV color space, VideoScope uses the following equations:

    Y = 0.299*R + 0.587*G + 0.114*B   Normalized range: 0% to 100%
    U = B - Y                         Normalized range: -88% to +88%
    V = R - Y                         Normalized range: -70% to +70%

The R, G and B components have a resolution of 8 bits. The resulting Y, U and V components are normalized and shown in the scope display as percentages, rounded to the nearest integer.

Note: When in Blue Only mode (see Front Panel Controls below) the R and G components are ignored and Y is calculated simply as B.

The front panel controls provide easy access to virtually all of VideoScope’s functionality. All controls have a keyboard shortcut, shown in parentheses. The front panel controls are grouped into four main sections:

Input Section

Source (I)

Selects the input source. Video Input and Reference sources are available. By default, the reference source is a standard color bar. To use a different reference source, paste a PICT image from the Clipboard, open any QuickTime movie or image file from the File menu, or drag the file into the VideoScope window.

Standard (S)

Selects the input standard. NTSC and PAL standards are available from the front panel. To use another standard (such as SECAM) choose ‘Video Input…’ from the ‘Options’ menu.

Freeze (F) or (Space)

Freezes the input source. Freeze is automatically released if the input source or standard is changed, or if the reference source is changed.

Blue Only (B)

Selects whether only the blue channel of the source video is displayed and analyzed. When Blue Only is selected, the waveform Y mode calculates Y as being the amount of blue in the source, ignoring the red and green components.

Adjust Section

Adjust (Up/Down Arrows)

Selects which image control value is to be adjusted. Image controls are only available for the Video Input source. The image controls available depend on the capabilities of the video digitizer being used. The currently selected image control is hilited in the panel. Numeric values can be entered directly using the numeric keypad.

Increase (Right Arrow, Option + Right Arrow)

Increases the currently selected image control value by 1% (or 10% if the option key is down).

Decrease (Left Arrow, Option + Left Arrow)

Decreases the currently selected image control value by 1% (or 10% if the option key is down).

Default (Clear)

Resets the currently selected image control value to the default value supplied by the video digitizer.

All Default (Option + Clear)

Resets all image control values to the default values supplied by the video digitizer. All Default only functions when an image control value is hilited.

Scope Section

Mode (Y, U, V, X)

Selects the scope mode. Waveform Y, U and V modes and a vector UV mode (whose keyboard shortcut is X) are available.

Mix (M)

Selects whether the incoming video is mixed with the scope display. Mix can also be enabled and disabled by dragging the video display in or out of the scope display. Mix is not available in UV mode since there is no horizontal relationship between the video and scope displays.

Color (C)

Selects whether the scope display uses the actual color of the sampled pixels when displaying Y, U and V waveforms.

Cursors (K)

Selects the cursor mode. The Y/U/V Value cursor is available in all modes, and shows the value of Y, U or V corresponding to the current pointer position. In the UV mode, the saturation percentage S is also displayed. The Sample Position cursor is available only in Y, U and V waveform modes, and shows the position of the sampled pixels in the source corresponding to the current pointer position.

Limits (L)

Selects whether minimum and maximum values are shown in the scope display. For the Y, U and V modes, limits can be either Instantaneous (calculated for each frame) or Accumulative (calculated over a sequence of frames), and are shown as cursors in the scope display. In the UV mode, only Accumulative limits are available, where the color space diagram accumulates successive frames showing the range of hue and saturation. Limits are automatically reset when the limits mode is changed.

Reset (R)

Resets the accumulated limits for the current mode.

Display Section

Display (D)

Selects whether performance statistics and other messages are shown in the display panel. When enabled, the average frames per second (FPS) and average analysis time per frame in microseconds (µS/frame) are displayed.

The File, Edit and Options menus allow you to open image files, copy and paste video and scope displays between applications, and provide access to QuickTime settings not available through the front panel.

File Menu

Open…

Opens any QuickTime movie or image file for use as the reference source. VideoScope uses QuickTime to open image files, allowing you to open a variety of formats such as JPEG, TIFF, BMP, GIF etc. Movies and images larger than 320x240 are scaled down to fit within 320x240.

Close

Closes the VideoScope window and then quits VideoScope.

Quit

Quits VideoScope. Front panel settings are automatically saved, and are restored the next time you use VideoScope.

Edit Menu

Copy RGB Video

Copies the contents of the RGB Video display to the Clipboard.

Copy YUV Scope

Copies the contents of the YUV Scope display to the Clipboard.

Paste

Pastes PICT data from the Clipboard into the reference source. The Paste command is only available when the Clipboard contains PICT data. Pictures larger than 320x240 are scaled down to fit within 320x240.

Clear

Clears the reference source. The reference source will revert to the standard color bar.

Options Menu

Video Input…

Displays the QuickTime settings dialog. Use this command if you need to access video digitizer controls other than those available via the front panel controls.

Luminance Spot Measurements

If the Option key is held down and the mouse button is clicked within the incoming video, the average luminance Y (or B if in Blue Only mode) of the 3x3 pixel area at that location is displayed. The spot measurement is cleared when the mouse button is released. However, if the spot measurement is dragged to a different part of the incoming video, another spot measurement is created. If the two measurements are within 5% of each other, the sample area will be shown filled instead of outlined. Dual spot measurements remain active allowing the image controls to be adjusted (useful when using a signal generator to calibrate the video digitizer). To clear dual spot measurements, hold down the Option key and click anywhere in the incoming video.

Magnification

If the Shift key is held down (or Caps Lock is enabled) and the mouse pointer is within the RGB or YUV displays, the area of incoming video or scope display around the cursor is magnified to 2 times its previous size.

Drag-and-Drop Support

The contents of the RGB display or YUV display can be dragged to the Desktop, a Finder window or any Drag-and-Drop aware application. By default, VideoScope’s cursors are not saved. To include cursors in the dragged image, hold down the Control key when dragging.